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(CNN)What began as a story about flooding, environmentalist groups say, has become about preventable environmental disaster.

Coastal Houston is the site of a large concentration of chemical plants, refineries, superfund sites and fossil fuel operations. Some have suffered damage from Hurricane Harvey, releasing toxic compounds into the environment, and environmentalists, in turn, are pointing the finger at politicians and industry leaders who have sought to ax regulations.

Specifically, they're criticizing the Environmental Protection Agency for delaying a chemical plant safety rule once President Donald Trump took office. In part, the rule would have ensured first responders knew what chemicals they may come in contact with and how to handle those chemicals in an emergency response situation.

The intention was to help prevent and mitigate chemical accidents.

"The rules that were delayed were designed to reduce the risk of chemical releases," said Peter Zalzal, special projects director and lead attorney at Environmental Defense Fund. "This kind of situation underscores why we shouldn't be rolling these rules back."

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Earlier this year, legislation was introduced in both the House and Senate that would repeal an EPA rule.

A report in the International Business Times noted the bill was cosponsored by a hefty handful of Texas Republican House members, and the companion bill in the Senate had the backing of both Texas Sens. John Cornyn and Ted Cruz.

Many who cosponsored the legislation, IBT noted, have accepted donations from the chemical industry, the American Chemical Council and Arkema, Inc.

Arkema

Thursday morning, the Arkema chemical manufacturing and storage facility outside of Houston burst into flames, and black smoke billowed out after Harvey's floodwaters knocked out equipment used to keep the plant's volatile chemicals cool. Fifteen sheriff's deputies were taken to the hospital for inhaling the irritants and a mandatory evacuation is in place for all residents living within 1.5 miles of the chemical plant in southeast Texas.

Friday afternoon, a fire broke out at the Crosby, Texas chemical plant.

The Crosby plant produces liquid organic peroxides used primarily in the production of common consumer products ranging from headlights assemblies for the automotive industry, to PVC for pipes, packaging and siding.

Arkema and its industry trade organization, the American Chemistry Council, had filed comments objecting to several of these key components of the proposed Obama-era chemical safety rule. The stricter rules for chemical plants like Arkema would have taken place March 14, but following the industry opposition, EPA chief Scott Pruitt delayed the Obama-era rule until 2019.

In a statement to CNN, the EPA said the agency's Risk Management Plan rule for chemical plants like Arkema is in effect, and "is an important safety rule that requires facilities that use extremely hazardous substances to develop plans that identify potential effects of a chemical accident, identify steps a facility is doing to prevent an accident, and spell out emergency response procedures, should an accident occur."

But the Obama-era amendments to the existing rule were stricter and were intended to strengthen the existing rule. The amendments revised several accident prevention requirements as well as what must be communicated to local authorities and the public.

To that, the EPA said: "None of the major amendments would have been effective until March 2018 and most well after that. The agency's recent action to delay the effectiveness of the 2017 amendments had no effect on the major safety requirements that applied to the Arkema Crosby plant at the time of the fire."

The Chemical Safety Board said in a statement that it would investigate the Arkema explosion.

Plants around the area

Many of these plants and refineries are located in low-income communities.

The Sierra Club created a map detailing some of the major operation the group says pose heightened threats to the 25 counties most affected by Harvey.

Sierra Club organizer Bryan Parras grew up in Houston and said as long as he could remember, industrial operations filled the city, posing environmental and health risks.

"These sites have caused devastation for my family, my friends and my neighbors for years, polluting our air and water with deadly toxins," Parras said. "Hurricane Harvey didn't create the problem my community faces, but it has magnified it."